74 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. III. 



Chapter III. — Sub-Himalayan Series— The Subathu Group. 



It has been shown in the preceding Chapter that we cannot yet 

 affirm, with any degree of certainty, to what age any of the stratified 

 rocks of the lower Himalayan region belong, — from lowest Tertiary to 

 oldest Palaeozoic. The truly historical portion of the record begins with 

 the Subathu Group. A glance at the map will show the limited exten- 

 sion of this group, which is the lowest member 

 Position and extension. 



of the great Sub-Himalayan series. With two 



very local exceptions, to be specially noticed, it is limited to the region 



between the rivers Jumna and Sutlej, that region which we have already 



seen marked by peculiarities in the arrangement of the lower Himalayan 



rocks. I will defer the discussion of this actual limitation to the end 



of this Chapter, as being the result of phenomena subsequent to the 



deposition of the formation. 



The succession of deposits, which I have provisionally ranked under 



one name as the Subathu Group, exhibits a very 

 General composition. . 



consiaerable diversity 01 mineral characters. In 



the bottom portion we find almost exclusively the finest description of 



sediments ; a yellowish brown silt may be taken as the characteristic 



rock* In the succeeding portion of the formation, a gritty, lumpy, bright 



red clay is predominant : these clays are slightly gypsiferous. Fine 



grained, massive sandstones greatly preponderate in the upper part of the 



croup. The united thickness of all can scarcely be less than 3,000 feet. 



There can be no doubt that this formation represents a very prolonged 



period of deposition, involving, as is shown by the 

 Considered as one group. 



change ol composition, a very considerable alteration 



of conditions. Nevertheless, pending the collection and examination of 



* I fail to recognize in the Subathu section the rocks spoken of by D'Archiac as " Marnes 

 noires" and " psammite." 



